Recycling B₄C grinding waste to fabricate high-performance ceramics by modification treatments and hot pressing

B₄C grinding waste, originated from the fine grinding process of sapphire wafers, is discarded without reutilization, which causes environmental pollution and resource waste. This work proposes new methods on recycling B₄C grinding waste to fabricate high-performance ceramics by first modification treatments via ball-milling mixing or microwave digestion with sulfuric acid and then hot pressing. The characteristic of B₄C grinding waste is studied and Al₂O₃ is the main impurity. The direct hot pressing of B₄C grinding waste is performed and the obtained ceramic is fragile. The large-size and unevenly distributed Al₂O₃ is verified to cause the fracture according to the structure analysis. Ball-milling mixing can break the Al₂O₃ agglomerate and make Al₂O₃ distribute evenly, and microwave digestion with sulfuric acid can remove most Al₂O₃. The ceramics fabricated via hot pressing with B₄C grinding waste treated with ball-milling mixing or microwave digestion show good microstructure and mechanical property. The relative density, hardness, flexural strength and fracture toughness of the ceramics fabricated with grinding waste treated with ball-milling mixing are 98.82%, 32.42 GPa, 439.44 MPa, 4.82 MPam^1/2, respectively, higher than those of the ceramics fabricated with grinding waste treated with microwave digestion, which are 98.69%, 29.54 GPa, 368.18 MPa, 4.20 MPam^1/2, respectively. This work not only realizes the secondary utilization of waste and avoids pollution, but also provides another way supplying the high-cost B₄C powder and ceramic, which has high economic benefits.